Field of the Invention
The present invention relates to a vibration device, and more particularly, to a vibration device for a mobile terminal, which generates vibration using piezoelectric effect.
Description of the Related Art
Recently, as virtual reality technology is developed, users increasingly desire more detailed and realistic information through virtual reality. One of the technologies developed to satisfy users' desires is haptic technology which transmits tactile sense and force. Such haptic technology is not only used for notification function using a vibration motor in a mobile phone, but also is widely used in various fields such as medical simulators, game devices or the like.
Specifically, a haptic device as well as a monitor and a speaker will be installed to a computing apparatus as an essential output device. This is because installing a haptic device to a portable electronic apparatus provides advantages of high perception of tactile stimuli and superior interoperability with IT apparatuses.
A vibration motor of a mobile terminal, which is a concrete example of a haptic technology applied to a portable electronic apparatus such as a smartphone, may enable a user to vividly feel vibration by adding vibration to a sound and an image output from a mobile terminal.
In general, a conventional vibration motor employed to a mobile terminal is a vibration generator using weight eccentricity, which simply vibrates the whole mobile terminal. A vibration device using an eccentric rotating mass (ERM), which is configured to vibrate by rotational eccentricity of a motor, has a response speed of about 200 ms. However, this response speed is quite insufficient to satisfy a user's demand for operational simultaneity.
Another example of a vibration motor employed to a mobile terminal is disclosed in Korean Patent Registration No.10-0793682, “MICRO LINEAR VIBRATION DEVICE” (cited reference 1). A linear vibration motor described in the cited reference 1 is configured to vibrate by vertical linear movement using a coil and a magnet, and has a response speed of about 50 ms. This response speed is greater than that of the ERM, however, it is still insufficient to satisfy a user's demand for operational simultaneity and cannot transmit slight vibration to a specific body part such as a fingertip.
In order to realize a haptic function optimized to a portable electronic apparatus, various vibration patterns including strong vibration, slight vibration and the like should be controlled to have an extremely high response speed. However, a vibration device configured with an ERM using rotational eccentricity or a linear motor using vertical linear movement just provides simple vibration.
Therefore, it is required to develop a vibration device for a mobile terminal, which can be precisely controlled to have a high response speed capable of satisfying diverse and complicated functions and can transmit slight vibration to a local body part such as a fingertip.